Упростите выражение cos20*cos40*cos80

Question

Упростите выражение cos20*cos40*cos80

Answer 1

= (cos20*cos40*cos80*sin20)/sin20=(1/2sin40*cos40*cos80)/sin20=
(1/4sin80*cos80)/sin20=1/8sin160/sin20=1/8sin(180-20)/sin20=
1/8sin20/sin20=1/8